During the process of manufacturing a wafer, an inert gas (e.g., nitrogen) filling machine is required to fill inert gas into a wafer carrier. The conventional chassis for the carriers of 200 mm-diameter wafers produced by the two largest manufacturers of 200 mm-diameter wafer in the world, Asysyt™ and Empak™, there are provided with holes for inert gas filling purpose, but they still could not be airtight.
U.S. Pat. No. 4,995,430 by Bonora et al. discloses a latch mechanism which is disposed on the box door of a box and is used for engaging the box door with the box. The latch mechanism is operable in two stages. The first stage of operation moves latch members from a retracted position to an extended position. The second stage of operation engages latch members with latch surfaces to move the box door in a sealing direction. However, the latch mechanism does not have any airtight function.
To achieve an airtight effect, a sealing element (e.g., O-ring) must be utilized in the engaging interface between the wafer carrier case and the chassis, and further an engaging measure is applied to the interface (e.g., by screws) to eliminate gaps in the interface and to achieve the airtight effect. However, since the airtight effect in the prior art is primarily for maintaining a long term and stable airtight condition, the engagement and the condition thus performed cannot be varied. In addition, the prior art only provides a static and constant airtight effect, which does not meet those requirements associated with different airtight levels under both unlock/lock conditions of the wafer carriers. Further, the prior art cannot provide synchronically and quickly the airtight and de-airtight functions, and thus does not satisfy the requirements in the processes of filling the inert gas into the wafer carriers.
Therefore, when the wafer carrier is sealed, it should obtain a better airtight; on the other hand, when the wafer carrier is opened, it should balance the differential pressure between inside and outside of the wafer carrier so as to easily separate the chassis from the carrier, and to break the airtight quickly. Thus, an airtight device is needed to provide airtight and de-airtight functions quickly in response to opening and closing of a unlock/lock mechanism of the wafer carrier.